Problems with lagged turbo and exhaust systems

Main Question or Discussion Point

hello,
does any one know if lagging a turbo and exhaust system would cause failure of the turbo. my thought is that on the lagged turbos the heat can not disperse causing early failure due to expansion of the casing, bearings and shafts. could it also effect the oil viscosity ???

Not sure if it helps any, but the first generation of auto engine turbos about 25 years back had the problem of excess heat frying the turbo bearings after engine shutdown. So the suggestion was to not turn off the engine right after driving, but to let it idle for a minute. Longer term, I believe the fix was to add a little oil reservoir to the bearing circuit, so the system could cope with the extra heat.
Given that the exhaust gas turbine which drives the compressor can run red hot, it is unlikely that lagging the components will introduce extraordinary additional stresses.

Oil inside the turbine unit pretty much has to come from the bearings, so there is an expansion issue in your case.
Usually in these installations one tries to keep the compressor section as cool as possible, no matter what the turbine temperature, so the bearing does not see the full turbine heat.
So there might be some improvement if the bearing is left uncovered, so it can cool down at a better pace, but it may impact the lagging installation.
Separately, you are quite right that the oil viscosity declines substantially at higher temperatures. There are specialized formulations that maintain their properties at higher temperatures, used in aero engines particularly.
You may need to consider these if you cannot fix the problem with alterations to the setup.